Washington State - my husband and I are looking to rent a house. My mother will be visiting fairly frequently, so we would like to rent a place with an extra room so she can stay with us when she does come. However, we do not meet the required 3x rent income that most places require. Is it legal for my mother to sign the rent with us as a tenant so we can combine our incomes, even though she won't actually be living there? We have absolutely no debt, so we wouldn't have any issues paying the rent, we are just slightly below the required income.